Conversion from Steam to hot water.

joseph annon

Hello.




I have just started being the service plumber for a church that was converted from 2 pipe steam to hot water. I know a little bit about steam heating. The original steam lines were used as sleeves for copper piping in the basement area. Copper pipes are then connected to galvanized pipes in areas with little access. The original steam pipes from the boiler and back are 3".
My assumption is that the steam was piped in parallel and sloped back to the boiler location. From the piping I can see which is about 10% of the total piping for the radiators they did install one ball valve feeding one of the radiators.

New Boiler in 2015 it is a Vitogas 050 496KBTU Natural gas unit.
I was called for a boiler non firing which turned out to be a failed switch on the vent damper. Replaced the vent damper and the boiler resumed operation. The customer then noticed a small leak in a float vent on the boiler. I replaced the float vent and purged air from the system and restarted boiler. I got a call the next day and the boiler was running but no heat to the radiators. One zone pump had failed I replaced it. The flow through the radiators was minimal and not really getting heat to the radiators. The near boiler piping 2" copper piping to radiators is 1.25" copper.
There are three zones of radiators.
Each zone pump is a Grundfos UP15-58 set on high speed.
The pumps are on the supply manifold.
The boiler is piped in primary secondary piping. The boiler pump is a Grundfos UP26-99 set on high. All zones are calling and boiler is short cycling. Return temperatures from zones are in the 50 degree range. Supply is in 120 degree range. Boiler is set at 167 degrees. I turned off the boiler pump and isolated it and boiler promptly dropped and when I checked the radiators I was getting hot water through them.

My question is how do you guys size pumps and and set up for balanced heating.
I am considering a few things
1 is up sizing the zone pumps to something with low head high volume to increase flow through each radiator.
2 Checking the valves on the radiators and see if they can be used to balance the flow for each zone. The hope is that the valves are all functional but expectation is that several will have to be replaced.
3 installing a control system to protect the boiler from extended runs at condensing temperatures.

Jamie Hall

You definitely need more flow through the radiators. Your delta T shows that. However, it may not be quite as simple as sticking a bigger flow pump on. You need to make sure that the steam conversion was done properly. Were all the radiator valves changed or might some of them be steam throttling valves? Were any -- or all -- of the radiators equipped with flow control orifices? If so, were they removed? Did anyone think to check? Were all of the traps on the outlets removed, or at least their internals removed?

And then... it's highly unlikely that the flow to various zones is even remotely balanced. Steam didn't need that; you do.

EBEBRATT-Ed

Ask the owner if the system ever worked after the conversion, did the radiators ever heat well?

Have you blead the radiation and checked the pressure on the system and checked the expansion tank?

Steamhead

This is why we don't do these conversions.

How long ago was this conversion done?

joseph annon

First of all thank you for the information.
I would not recommend conversion from steam to hot water from the little I know about steam.
From what I can tell it has not heated well for a long time. They have a lot of portable electric space heaters in what appears to me the end runs of the radiators. Probably since the conversion which was done in 2005.
I see no signs that any work was done on the radiators, All valves and connections and manual vents at the radiators look original to me. Or at least pre-conversion.

I checked the radiators that have have coin vents and they all push water only. Some radiators are fed with over head piping. They have no vents. However they were all heating. Expansion tank is good. It is bladder type. I will have to see if the piping under floor is accessible and see if I can locate the traps. The radiators seem to be of two different types. Mostly that some are wider per section and more ornate than others. I will get some photos of them.

I knew that there was a lot I did not know about steam. Steam heat is rare here. There are a few residences that I know and some commercial buildings. I don't personally know any plumbers who work on steam.

It seems that there is a lot to check to see if the conversion was done correctly. I will talk to the customer and see how much they want me to do.